Yorkshire Water has appealed to farmers around land near the River Derwent to carefully manage the use of slug control pesticides to reduce the impact they have on tap water quality.
The pellets can occasionally leak into watercourses in East Yorkshire that flow into the river, particularly near Stamford Bridge, Loftsome and Pocklington.
Slug pellets are commonly used by farmers during this time of the year to control slug infestations, which risk eating away at crops and damaging food production.
However, an active ingredient – metaldehyde – can sometimes runoff from the farmland or flow through field drains into the watercourse. Although this poses no danger to health or the environment, metaldehyde levels in the River Derwent have occasionally breached EU drinking water standards.
Trials in some parts of the United Kingdom have shown that 98.7% of metaldehyde contamination within rivers and streams comes via flowing field drains.
Andrew Walker, catchment strategy manager at Yorkshire Water, said: “We are positively working with farmers on this issue as we recognise the demands they have to meet food production targets.
“So we are not saying to farmers to stop using slug pellets, but instead to ensure they are applied correctly and to consider alternative measures that have a lower water impact. This way, crops will be protected from nuisance slugs without adversely affecting raw water supplies.”